Concept:The brother’s age is Kobby’s age minus the age difference.Explanation:Let the brother’s age be x years.Kobby is 5 years older than his brother.So Kobby’s age is x+5.Kobby is 13 years old.Therefore, 13=x+5.Subtract 5 from both sides to find x.x=13−5x=8Thus, the brother is 8 years old.Answer:Option B. 8 years.